DOE OSTI2020
Pr2TiO5 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Pr3+ sites. In the first Pr3+ site, Pr3+ is bonded to seven O2- atoms to form distorted PrO7 hexagonal pyramids that share corners with two equivalent PrO7 hexagonal pyramids, a cornercorner with one TiO5 trigonal bipyramid, edges with seven PrO7 hexagonal pyramids, and edges with two equivalent TiO5 trigonal bipyramids. There are a spread of Pr–O bond distances ranging from 2.44–2.49 Å. In the second Pr3+ site, Pr3+ is bonded to seven O2- atoms to form distorted PrO7 hexagonal pyramids that share corners with two equivalent PrO7 hexagonal pyramids, corners with three equivalent TiO5 trigonal bipyramids, edges with five PrO7 hexagonal pyramids, and edges with two equivalent TiO5 trigonal bipyramids. There are a spread of Pr–O bond distances ranging from 2.38–2.53 Å. Ti4+ is bonded to five O2- atoms to form distorted TiO5 trigonal bipyramids that share corners with four PrO7 hexagonal pyramids, corners with two equivalent TiO5 trigonal bipyramids, and edges with four PrO7 hexagonal pyramids. There are a spread of Ti–O bond distances ranging from 1.79–2.03 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded to three Pr3+ and one Ti4+ atom to form distorted OPr3Ti tetrahedra that share corners with eight OPr3Ti tetrahedra and edges with three OPr4 tetrahedra. In the second O2- site, O2- is bonded to four Pr3+ atoms to form OPr4 tetrahedra that share corners with twelve OPr3Ti tetrahedra and edges with three OPr4 tetrahedra. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two Pr3+ and two equivalent Ti4+ atoms. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Pr3+ and one Ti4+ atom. In the fifth O2- site, O2- is bonded to three Pr3+ and one Ti4+ atom to form a mixture of edge and corner-sharing OPr3Ti tetrahedra.